This disclosure relates to gas turbine engines, and more particularly to a starter air valve system with dual electromechanical controls for gas turbine engine motoring.
Gas turbine engines are used in numerous applications, one of which is for providing thrust to an airplane. When the gas turbine engine of an airplane has been shut off for example, after the airplane has landed at an airport, the engine is hot and due to heat rise, the upper portions of the engine will be hotter than lower portions of the engine. When this occurs thermal expansion may cause deflection of components of the engine which can result in a “bowed rotor” condition. If a gas turbine engine is in such a bowed rotor condition, it is undesirable to restart or start the engine.
One approach to mitigating a bowed rotor condition is to use a starter system to drive rotation (i.e., cool-down motoring) of a spool within the engine for an extended period of time at a speed below which a resonance occurs (i.e., a critical speed or frequency) that may lead to damage when a sufficiently large bowed rotor condition is present. However, it can be challenging to repeatedly use a starter system to hold the engine speed below a typical starting speed for an extended period of time, as starter systems are typically designed to fully accelerate the engine beyond the critical speed to reach the starting speed. Using a typical starter system for an extended motoring time below the critical speed may result in increased component wear, component service life reduction, and/or increased reliability concerns.